Historically, lubricating oil products for use in applications such as automotive engine oils have used additives to improve specific properties of the basestocks used to prepare the finished products. With the advent of increased environmental concerns, the performance requirements for the basestocks themselves have increased. For example, American Petroleum Institute (API) requirements for Group II basestocks include a saturates content of at least 90%, a sulfur content of 0.03 wt. % or less and a viscosity index (VI) between 80 and 120. Currently, there is a trend in the lube oil market to use higher quality basestocks in order to meet the demand for higher quality products that provide for increased fuel economy, reduced emissions, etc.
Conventional techniques for preparing basestocks such as hydrocracking or solvent extraction require severe operating conditions such as high pressure and temperature or high solvent:oil ratios and high extraction temperatures to reach these higher basestock qualities. Either alternative involves expensive operating conditions and low yields.
Hydrocracking has been combined with hydrotreating as a preliminary step. However, this combination also results in decreased yields of lubricating oils due to the conversion to distillates that typically accompany the hydrocracking process.
In U.S. Pat. No. 5,573,657, a hydrogenation catalyst, and process using the same, is described wherein a mineral oil based lubricant is passed over a mesoporous crystalline material, preferably with a support, containing a hydrogenation metal function. The supported mesoporous material has pore diameters greater than 200 Å. The hydrogenation process is operated such that the product produced therein has a low degree of unstaturation.
However, there is still a need in the art for an effective process to prepare quality lubricating oil basestocks.